A conventional echocardiographic study is performed on the chest of a patient using a hand-held high frequency or ultrasound transducer for achieving a non-invasive examination of cardiac structures, function, and flow patterns. In some cases, however, the transducer beam cannot adequately image a particular cardiac structure or area due to the thickness of a patient's chest wall, surgical dressings positioned on the patient's chest wall, or a medical condition such as a chronic lung problem (emphysema).
A solution to these limitations in echocardiographic study is the transesophageal technique, which utilizes a miniaturized echotransducer positioned on the tip of a steerable gastroscope shaft. This transducer is introduced into the esophagus through the mouth, and the echocardiographic study is performed through the esophageal wall or stomach by directing the transducer beam toward the heart. A transesophageal echotransducer, which is commonly 14 by 13 mm in rectangular cross-sectional dimension, is traditionally positioned on the distal end of a gastroscope and inserted into the esophagus adjacent the heart. The transducer is moved and repositioned for attaining various images. In addition, a transducer is often removed and replaced with a different transducer for imaging a different angle, particularly since small bi-plane transducers are not commercially available.
A problem with the introduction and positioning of a transducer in the esophagus of a patient is that transducer movement causes gagging and considerable discomfort to conscious patients. As a result, sedation or even general anesthesia is used. Furthermore, transducer movement causes trauma to the esophagus as well as other complications such as aspiration, respiratory depression, esophageal perforation, and bleeding. Several anatomical structures, such as a sphincter, the lateral piriform recesses near the cricopharyngeal region, and the right angle arrangement between the mouth floor and the esophagus in the pharynx, present problematic areas for the physician to negotiate during the introduction, positioning, and exchange of a transducer.
A possible approach to minimizing these negative effects is to introduce a transducer through an endotracheal tube, which is conventionally used for establishing or maintaining an airway in a patient with respiratory problems. A limitation of endotracheal tubes is that they are used for providing an airway lumen. As a result, endotracheal tubes typically have a relatively small inside diameter and are formed of relatively stiff and unkinkable material. Therefore, endotracheal tubes are unsuitable for protecting the esophageal wall during introduction, positioning, and exchange of one or more transducers therethrough.